1. Field of the Invention
The present invention relates to relays, and more particularly to a direct current high voltage control relay employable in a circuit necessary to interrupt a high-voltage direct current.
2. Description of the Related Art
A high-voltage direct current flows through some circuits such as a circuit near the battery of an electric car and the circuit of an uninterruptible power supply (UPS) that is activated to supply power to a computer system in the case of an outage of commercial power to the computer system.
In the case of applying a relay to such circuits, when the paired contacts of the relay in contact with each other are separated from each other, an arc current flows between the contacts because of the action of a high voltage on the relay, and this arc current damages the contacts so as to reduce the useful service life of the relay.
A unit that opens and closes the high-voltage direct-current circuit of the UPS includes a combination of a relay and a semiconductor switch. The semiconductor switch reduces the value of a current flowing through the relay so as to prevent an arc from being generated between the contacts of the relay at the time of opening the circuit.
However, according to this configuration, the semiconductor switch is required in addition to the relay so as to increase the number of components. This is a problem in terms of reliability and also increases cost.
Japanese Laid-Open Patent Application No. 2001-176370 shows a relay to be applied to a circuit near the battery of an electric car. According to this relay, a permanent magnet is provided near contacts so as to deflect an arc current generated at the time of separation of the contacts using the magnetic force of the permanent magnet, thereby preventing the contacts from being damaged and increasing the durability of the relay. Further, according to this relay, a pair of contact sets are arranged side by side, and the arc current generated between one of the contact sets and the arc current generated between the other one of the contact sets are deflected outward so as to be away from each other.
This relay, however, is provided in the middle of a circuit interconnection that connects one electrode, for example, the positive terminal of a direct-current power supply and a load circuit, and the above-described paired contact sets are connected in parallel in the circuit interconnection.
Therefore, even when the two contact pairs of the relay are open, the negative terminal of the direct-current power supply and the load circuit remain connected, so that the direct-current power supply and the load circuit are not completely independent of each other. As a result, there is the risk of continuously supplying current to the load circuit particularly when the ground potential is unstable.
Further, the above-mentioned relay is a terminal connection type and is large in size. Further, the above-mentioned relay is not so configured as to be mountable on a printed circuit board.
Japanese Laid-Open Patent Application No. 10-326553 shows a relay having a pair of contact sets and a permanent magnet provided between the paired contact sets and configured to be mountable on a printed circuit board. However, the arc generated at each contact set is not blown off outward, nor are the circuit interconnections extending from the positive terminal and negative terminal, respectively, of a direct-current power supply simultaneously broken.